Field of the Invention
The present invention relates to a voltage supply unit and a display device having the voltage supply unit.
Discussion of the Related Art
Recently, various display devices have been developed which can decrease in weight and volume which are demerits of cathode ray tubes. Examples of the display devices include a liquid crystal display device, a field emission display device, and an organic light-emitting display device.
A display device includes a display panel that has data lines, gate lines, and pixels coupled to the data lines and the gate lines, a gate driver supplying gate signals to the gate lines, a data driver supplying data voltages to the data lines, and a voltage supply unit supplying drive voltages to the gate driver and the data driver. Each pixel receives a data voltage from a data line when a gate signal of a gate-high voltage is supplied to each pixel from a gate line, and emits light with predetermined brightness depending on the data voltage.
When the display device is powered off, a voltage input to the voltage supply unit is cut off and thus the voltage supply unit does not supply the drive voltages to the gate driver and the data driver any more. When the display device is powered off and the data voltages supplied to the pixels are not discharged, the data voltages may remain in the pixels. In this case, even when the display device is powered off, the display panel displays an afterimage or an abnormal image during a predetermined period of time due to the data voltages remaining in the pixels. In order to prevent this phenomenon, the display device controls the gate driver in a discharge mode using a discharge signal when the display device is powered off. The gate driver is controlled to supply the gate signals of a gate-high voltage to all the gate lines during a predetermined period of time in the discharge mode. In this case, since the data voltages remaining in the pixels are discharged to the data lines, the display panel does not display an afterimage or an abnormal image.
On the other hand, when the display device is driven in a sleep mode or firmware is refreshed after being updated, or due to unknown errors, there may occur a problem in that a discharge signal controls the gate driver in the discharge mode even when the voltage supply unit normally supplies the drive voltages to the gate driver and the data driver. In this case, even when the display device is not powered off, the gate driver performs an abnormal driving operation of supplying the gate signals of a gate-high voltage to all the gate lines. When the gate driver performs the abnormal driving operation, the gate driver requires a current much higher than that when the gate driver performs a normal driving operation, and thus the voltage supply unit supplies the gate driver with a current which is much larger than that when the gate driver performs the normal driving operation. At this time, when the abnormal driving operation of the gate driver is continuously performed for a predetermined period of time, there may occur a problem in that the current supplied from the voltage supply unit to the gate driver is not recovered to the original state even when the discharge signal does not control the gate driver in the discharge mode any more. In this case, the display device continuously displays an abnormal image.
Since the voltage supply unit supplies the gate driver with a current which is much higher than that when the gate driver performs a normal driving operation, there may occur a problem in that a component is damaged, for example, a resistor of the voltage supply unit is burnt.